The method of decontamination waste ion-exchange resin from the storage tank of radioactive waste from nuclear power plants

 

The invention relates to nuclear energy, in particular to the processing technology of ion-exchange resin. The inventive through the spent cation exchange resin miss decontamination solution having a temperature of from 30 to 100oWith, including the sodium salt and acid. Then do the cleaning of the received decorate on the filter with ferrocyanide sorbent, and by alkalizing solution until a pH equal to 9,5-11,0 additionally carry out the deposition of decorate two - and trivalent radionuclides. Advantages of the invention are to increase the efficiency of desorption of radionuclides from the cation exchanger and increase the quality of cleaning decorate from activated corrosion products. 1 C.p. f-crystals, 1 Il.

The invention relates to nuclear energy, in particular to the processing of radioactive waste from nuclear power plants (NPPs).

The proposed method can be used for processing of the cation, and processing the mixture of cation and anion exchange resin without their separation, and if the cation is contaminated not only with radionuclides of cesium, but also activated corrosion products - two - and trivalent radionuclides (cobalt, manganese, retrostyle, including the removal of radionuclides cation exchanger passing through him decontamination solution in the form of a dilute solution of nitric acid and purification of the obtained dirty solution from radionuclides on ferrocyanide sorbent [1].

The disadvantages of this method are the low efficiency of desorption from the cation exchanger of radionuclides and sorption last ferrocyanide sorbent from the dirty decontamination solution, and the impossibility of using the method for the purification of cation exchange resin contaminated activated corrosion products.

Closest to the proposed solution to the technical essence and the achieved effect is taken as a prototype method of decontamination ion-exchange resin from a storage tank of liquid radioactive waste from nuclear power plants (ha NPP), including the removal of radionuclides cation exchanger passing through an ion-exchange resin decontamination solution in the form of a mixture of sodium salt and acid and purification of the obtained dirty decorate from radionuclides on the filter with ferrocyanide sorbent [2].

This method provides effective cleaning of the cation from radionuclides of cesium, but no cleaning dirty decorate from two deposits - reduction of radioactive waste or controlled storage, by increasing the efficiency of desorption of radionuclides from the cation exchange resin in the presence of anion exchange resin and increase the cleaning dirty decorate from activated corrosion products.

To solve this problem in the way, including the removal of radionuclides cation exchanger passing through an ion-exchange resin decontamination solution in the form of a mixture of sodium salt and acid and purification of the obtained dirty decorate from radionuclides on the filter with ferrocyanide sorbent, additionally carry out the deposition of dirty decorate two - and trivalent radionuclides by alkalizing the solution to adjust the pH to the value selected in the range from 9.5 to 11.0, and the temperature of the decontamination solution is chosen in the range from 30 to 100oC.

Thus, before decontamination waste ion-exchange resin from the storage tank are circulation decontamination solution through the storage tank and the filter ferrocyanide sorbent.

We found that within concentrations of iron, desorbed from the resin in the decontamination solution, characterized dirty desideria cobalt with iron hydroxides takes place in the interval of pH from 9.5 to 11.0, moreover, when the pH of the solution above 11,0 there is a partial destruction ferrocyanide sorbent.

At values of pH below 9.5 coprecipitation process ineffective.

The temperature increase has a positive effect on the completeness of desorption, as well as on the rate of dissolution of magnetite formation in the phase of the cation. In addition, as shown by our study, the efficiency of sorption of cesium on ferrocyanide sorbent with increasing temperature also increases, since at low temperatures ferrocyanide sorbent inclined to disaggregation (peptization), with an increase in temperature, this process slows down, which provides a more complete sorption. When the temperature is the formation of larger particles of sediment that accelerates the deposition process and simplifies technology for the treatment of sludge.

At a temperature of 30oWith enough quality possible washing of the sorbent due to the effective desorption of radionuclides with ion exchange resins with a low level of activity.

Increasing the temperature above the 100oSince it is impractical because of the possibility of substantial destruction of the anion and the inconvenience of working in the field of intensive evaporation.

Use predvaritel reduce the initial radioactivity of the resins and to simplify subsequent decontamination procedure. In addition, pre-washing can reduce obluchaemoi staff.

The transaction method is determined by the specific pollution resins activated corrosion products. If specific pollution waste resin is largely determined by the presence of activated corrosion products (according to the "Basic sanitary rules for radiation safety (OSPORB-99) when the value of the specific activity60With more than 110-6CI/l), then the preferred preliminary deposition of dirty decorate radionuclides transition metals and the subsequent cleaning decantate from radionuclides of cesium on ferrocyanide sorbent.

When the value of the specific radioactivity of dirty decorate60With less than 110-6CI/l preferred pretreatment dirty decorate from radionuclides of cesium on ferrocyanide sorbent and subsequent deposition of corrosion products, allowing further cementing sediment to obtain low cement compound.

The drawing shows a circuit implementing the method.

The proposed method of desactivate what FL corrosion is significant, as follows.

A mixture of resins (used cation exchange resin and anion exchange resin) from the tank 1 ha hydrozagadka served in the filter 2, which is received and pre-cooked in the vessel 3 decontamination solution in the form of a mixture of sodium salt and acid with a pH lower than 0.7 and a temperature selected in the range from 30 to 100oC. In the filter 2, the radionuclides of cesium and metal corrosion group of the cation are moving in the decontamination solution. Deactivated resin can be stored as low-level industrial waste. Received dirty desorbed decontamination solution is collected in the tank 4 with the mixer, where it is then alkalinized by adding a solution of sodium hydroxide and calcium until the pH is selected in the range from 9.5 to 11.0. When this occurs, there is effective co-deposition of cobalt and other divalent or trivalent radionuclides with iron hydroxides.

Decanted decontamination solution from the tank 4 is sent to the filter ferrocyanide sorbent made in the form of the filter container 5, where the purification of decantate from radionuclides cesium.

Purified detectivesatoshi solution back into the tank 3, which is acidified with nitric acid to a pH of below 0.7 and re-use my storage and/or disposal.

The residue after curing (cementing) and the shutter speed for the decay of60With to activity values at which the product is removed from the radiation control can be placed on the landfill of industrial waste.

The whole process is carried out at a radioactivity monitoring environments using gamma spectral analysis in accordance with the radioactive safety Standards (NRB-99)".

For the case when the impurity resins activated corrosion products is negligible, the method is carried out similarly, but dirty desorbed decontamination solution is collected in the vessel 4 and the pH value of decorate adjusted to 1.8 to 2.0. This allows you to maintain the iron compounds and radionuclides corrosion group dissolved, and to keep the resource work ferrocyanide sorbent at an acceptable level of about 5000 column volumes.

From the tank 4 the solution is directed to the removal of radioactive cesium in the filter container 5.

Purified from radionuclides cesium decontamination solution is collected in the collecting tank 6. Then the container 6 add a solution of sodium hydroxide and calcium until the pH is selected in the range from 9.5 to 11.0, and the coprecipitation of radionuclides korrektirovki chemical composition of the solution is re-used.

Example 1. The mixture of spent resins (70% of the cation marks KU -2 -8 and 30% of the anion brand AB -17 -8) from the tank 1 ha loaded in the filter 2. The initial specific activity of the resin was as follows:137Cs - 2,0210-5CI/l,134Cs - 1,1110-5CI/l and60Co - 2,4310-6CI/l dose rate from the middle of the filter 2 2,8 Mr/hour.

Cooked in the vessel 3 decontamination solution of sodium nitrate and nitric acid with a pH of 0.5 and a temperature of 30oWith was passed through the resin in the filter 2 from the bottom up.

After passing 7 column volumes of decontamination solution dose rate from the filter 2 amounted to 0.04 Mr/h, the specific activity of the purified resin on137Cs - 3,410-10CI/l, which according to PP.3.11.4 and 3.11.11 OSPORB-99 allows you to place it on the landfill of industrial waste.

Dirty desorbed from the filter 2 has collected in the tank 4 and the addition of sodium hydroxide solution was adjusted pH decorate to 9.5.

Selected sediment was filtered, and decanted pass through the filter container 5 with ferrocyanide sorbent.

The specific radioactivity of the purified solution was137Cs less than 2,0

Example 2. Same as in example 1, but the process of decontamination in the filter 2 was carried out at the temperature of the solution 100oWith, and the process of co-precipitation of cobalt with iron hydroxides was carried out at a pH of 11.0.

The dose rate from the filter 2 is deactivated resin constituted of 0.015 Mr/hour. The specific radioactivity of the purified resin:137Cs is not detected,60Co - 5,910-9CI/L. the Specific radioactivity of the purified solution:137Cs is less than 210-10CI/l,60With not found.

Example 3. The mixture of spent resin of the same composition as example 1, but with a specific radioactivity in137Cs - 1,3210-5CI/l,134Cs - 7.0710-6CI/l and60Co - 4,5510-8Ku/l were loaded into the filter 2. The dose rate from the filter 2 was 1,99 Mr/hour. Decontamination of spent resin solution of the same composition as example 1 but at a temperature of 80oC.

After passing 7 column volumes of decontamination solution dose rate from the filter 2 is constituted 0.014 Mr/h, the specific activity D/chr/8226.gif">10-9CI/L.

Dirty desorbed from the filter 2 has collected in the tank 4, adjusted pH to 1.8 by adding sodium hydroxide and purified from radionuclides of cesium on the filter container 5. The filtrate is collected in the collecting tank 6 and was in the process of deposition of divalent or trivalent radionuclides bringing the pH to 10.5.

The specific radioactivity of the purified solution was:137Cs less than 2,010-10CI/l,60Co - 3,610-10CI/L.

Example 4. Same as in example 3, but before decontamination resin into the container 1 ha poured decontamination solution of the same composition as in the previous examples, the reported capacity 1 filter container 5 containing ferrocyanide sorbent, and spent the circulation of the solution within 8 hours.

Thus, the specific radioactivity of the spent resin was reduced to:137Cs - 1,4710-7CI/l and60Co - 4,110-8CI/L.

The specific radioactivity of the purified resin amounted to:137Cs is not detected,60Co - 2,010-9CI/L.

The specific radioactivity of the purified solution was neither the ri temperature of 20oC, and the deposition process when the pH of the solution to 9.0.

The dose rate from the filter with the purified resin constituted 0.08 Mr/hour. The specific activity of the purified resin:137Cs - 8,310-9CI/l and60Co - 9,210-9CI/L. the Total specific activity of the resin is greater than 110-8CI/l, which does not allow you to store it on the landfill of industrial waste.

The purified solution contained137Cs - 3,710-10CI/l and60With - 1,310-9CI/l, the efficiency of cleaning decontamination solution is low.

Sources of information 1. Patent UK 1533955, CL G 21 F 9/12, published. 1976.

2. Patent of the Russian Federation 1762666, CL G 21 F 9/12, published. 1996 - the prototype.

Claims

1. The method of decontamination waste ion-exchange resin from a storage tank of liquid radioactive waste from nuclear power plants, including the removal of radionuclides cation exchanger passing through an ion-exchange resin decontamination solution in the form of a mixture of sodium salt and acid and purification of the obtained dirty decorate from radionuclides on the filter with ferrocyanide sorbent that is different is selecive solution to adjust the pH to a value selected in the range from 9.5 to 11.0, and the temperature of the decontamination solution is chosen in the range from 30 to 100C.

2. The method according to p. 1, characterized in that before decontamination waste ion-exchange resin from the storage tank are circulation decontamination solution through the storage tank and the filter ferrocyanide sorbent.

 

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FIELD: recovery of liquid radioactive wastes.

SUBSTANCE: proposed method includes bringing liquid radioactive wastes in contact with matrix saturated with selective ion-exchange material (solid extracting agent). Glass-crystal material with open porous structure is used as matrix for the purpose. Matrix material is produced from hollow glass-crystal cene spheres formed from mineral particles of volatile ash produced as result of black coal combustion and saturated with selective ion-exchange material.

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5 cl, 1 tbl, 5 ex

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